I have read that ordinary (straight-tube, not CFL) fluorescent lights
can be dimmed to a certain extent (almost certainly not below 50%), but
will an ordinary electronic dimmer (using a Triac, I think) work for
this purpose? The dimmers now being promoted as specially for dimmable
CFLs and LEDs are too limited in their power-handling capacity. I'm
looking to dim a set of 16 x 4' tubes (four 4-tube fittings).
On 12/31/2014 10:46 AM, Percival P. Cassidy wrote:
In a nutshell, no. The fixture needs a dimmable ballast. A non-dimmable
ballast will not allow the lights to dim. Even though some lamps will
dim slightly, you will drastically shorten the life of both the lamps
and the ballast if you use a dimmer switch.
Many CFLs are dimmable because they have a dimmable ballast. LEDs are
dimmable because of the driver (similar to a ballast). Otherwise, they
would not work on a dimmer switch.
A regular dimmer can't be used.
FWIW, I was a photographer and moved to a loft space in a downtown office
building. When the space was being built out, the management insisted
that there be the same quantity of two tube 48" flourescent fixtures in
the suspended ceiling as there would be if the space was being used for an
I thought they would be way too bright but had no choice. I was
right...they were way too bright for my purpose so I bitched mightily to
the building management. They had the maintenance people replace one
(two?) of the tubes in the fixtures with what they referred to as a
"phantom" tube. I do not recall the ballasts being replaced, just the
tube (and I don't recall if it was one or both tubes) but I could be
wrong, it has been 40 years.
The result was markedly reduced light; not variable, just dimmer.
Phantom tubes are plain glass tubes with a bi-pin base to fit
fluorescent fixtures and a wire conductor in the center of the tube.
They produce no light and draw no power, but allow the fixture wiring
and ballasts to be untouched. This allows only one lamp to illuminate,
thus, reducing light output and dimming the room and/or area, depending
on how many are replaced.
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